: Wayner,: This is a gravity toilet, so water pressure should have little to do with it. : The flush valve uses two buttons, one to let out a little water, and the other allows more to drop out of the tank. : Have you removed the cover and checked to see why there seems to be no difference between the two flushes? Terry Love

Ok, on investigating this, I had a close look at the plastic mechanisms at the bottom of the tank. There appears to be a large, white, circular drain plug at the bottom of the tank. There is a hollow plastic shaft rising vertically up from the center of this big circular plug. This hollow shaft appears to be designed so that it moves independently, up and down, within the center of the big drain plug, like a pipe sliding inside a doughnut hole. The top end of this hollow shaft is the small square piece in the center of your photo.

When I press either of the buttons on the top of the tank, they hit those purple plungers, which hit a "see-saw" lever, which lifts the hollow shaft, which slides freely inside the "doughnut", and the toilet flushes. The diameter of the tank drain is, I assume, the same diameter of the hollow shaft, or about 1".

If I press and release either button quickly, the flush only drops the tank water level by 2". If I press and manually hold either button down for as long as the toilet tank will drain for, the flush will drain the level in the tank by about 5", but very slowly, with the usual pathetic flushing action in the bowl.

So, for an experiment, I grabbed the top of the hollow shaft directly by hand (ie. the hollow square end in your photo), and I lifted it manually, but I applied a bit of pressure off to one side. This time, when the shaft lifted, the side pressure caused friction on the shaft moving inside the doughnut hole, so that the doughnut itself was lifted from the tank floor. So, instead of about a 1" drain diameter in the tank floor, I now had a 4" drain diameter.

Whoooosh! Magic. First time EVER in 2 1/2 years of plumber and Caroma-dealer head scratching that this stupid thing has worked.

Ok, so now, I assume the "full flush" button is somehow not connected to the bottom "doughnut" to lift it during the "full flush". Is there any way to deal with that easily? The plastic mechanism doesn't look that easy to pull apart, or even remove from inside the tank.

I wish the Caroma web site had an exploded view of their proprietary flushing mechanism, since it's so odd that not even the dealers or local plumbers can figure it out. I'm not looking forward to trying to find replacement parts, if that's what you say I need.